Glad that the rescue thing has worked out for so many people here. But to just to temper the water a little….
Wife spent a lot of time and energy researching breeds/mixes/ages/shelters that would work for us (read: didn't just go get some random dog). When we went to the shelter, we told them we had two cats and that aggressive behavior was a deal breaker. 6 months later, a couple of grand in training, hundreds of hours spent working on the training (so long to that ride season), we had a dog that still was trying to kill our cats and that had drawn blood twice in seperate attacks and my wife's parents basically were scared to come stay with us (ok - maybe that last bit might have been a good thing). I finally had to take the dog back to the shelter and they said - well we told you she was aggressive.
If I went to a shelter again, I'd go with someone that knows dogs and can help spot any warning signs of a troubled dog, or if we were getting a young puppy that hasn't been broken by the shelter experience yet.
Again - glad it's worked for so many here, but when it doesn't work, it's a really shitty experience.
PS: and if the shelter tells you to use Bark Busters - turn around and walk out.